Along with the developments of high-speed and highly integrated semiconductor devices, a signal delay has caused a serious problem. The signal delay is represented by the product of the resistance value of wiring and the capacity between wirings as well as between layers, and in order to suppress the signal delay to the minimum, effective methods are to reduce the wiring resistance and also to lower the dielectric constant of an interlayer insulating film.
In recent years, with respect to the method for reducing the dielectric constant of the interlayer insulating film, a method has been proposed in which an interlayer insulating film containing a B—C—N bond is formed on a surface of a subject member by a plasma CVD process in an atmosphere containing a hydrocarbon-based gas, borazine and a plasma-based gas. Moreover, it is also disclosed that the interlayer insulating film exerts a low dielectric constant (see, for example, Patent Document 1 (Japanese Patent Laying-Open No. 2000-058538)).
However, in the above-mentioned conventional method, although a film having a low dielectric constant and high mechanical strength can be formed by using borazine as its material, no consideration is given to the moisture resistance thereof; consequently, when a film that has been formed is left, the film absorbs moisture to cause problems of failures in maintaining the dielectric constant and mechanical strength. Another problem is that the resulting film has a high leak current to cause an insufficient insulating property.    Patent Document 1: Japanese Patent Laying-Open No. 2000-058538